A recreational vehicle (hereinafter RV) is conventionally equipped with three tanks: a fresh water tank, a grey tank and a waste tank. In typical practice, the water tank is periodically filled with fresh water when available. The other two tanks are drained or dumped into facilities commonly provided at campgrounds, roadside parks, etc. In one form of draining and dumping operation, the grey and waste tanks are dumped and then a hose is connected to a source of water under pressure and water is directed into the tanks to flush out any remaining waste, etc. In the case of the waste tank, the hose is directed into the stool with the flush pedal valve open, a procedure that often results in overflow and resulting damage to the interior of the RV. Very often the aid of service personnel at the dumping facility is enlisted and possible errors and carelessness are multiplied.